1. Field of the Invention
This invention relates to new compounds containing independent peroxidic and aliphatic azo groups in the same molecule and to their use as sequential free radical generators in formation of polymers.
2. Description of the Prior Art
The combination of an azo group and a peroxide group in the same molecule, however, is not new. The following such compounds have been reported: ##STR1## where X',X'.sub.1,X'.sub.2,X'.sub.3 can be H--,NO.sub.2,NH.sub.2,I,C.sub.2 H.sub.5 O--, ##STR2## where R'.sub.1,R'.sub.2, and R'.sub.3 are organic radicals which are inert to azo and hydroperoxide radicals.
None of these known azo-peroxides are useful as sequential free radical generators and such a use for these compounds has not been suggested. Compound (2) has been reported to be a low temperature polymerization initiator. Compounds (3) and (4) have also been reported to be initiators of vinyl polymerization. Compounds of structure (5) are reported to be photo- and thermalpolymerization initiators i.e. they will generate free radicals either by irradiation or by heating, which is typical for conventional azo and peroxide initiators. In each of these compounds (1), (3), (4) and (5), the peroxy and azo groups are attached to the same carbon atom. Thus, these compounds undergo simultaneous azo and peroxide decomposition and consequently cannot be used as sequential free radical generators in the manner that the novel compounds of the present invention can be used. The compounds of this invention contain azo and peroxide groups which are not linked to the same carbon atom and therefore sequential decomposition can and does occur, as illustrated in the Examples.
In compound (2), the azo portion of the molecule is not a free radical generator, at least in the broad temperature range where vinyl polymerizations are conventionally carried out. The peroxide portion is a free radical generator useful for vinyl polymerizations. The azo portion in this structure is attached to two phenyl or substituted phenyl radicals and structures of this type are typical azo dyes. These structures are known to be stable and absorb certain wavelengths of visible light. Thus, the azo portion of compound (2) can be used to activate the peroxide portion by visible light and it can also be used as a dye to impart color, but it does not decompose to give free radicals under conventional vinyl polymerization conditions. Compounds of structure (2) cannot be used as sequential free radical generators in the manner that the novel compounds of the invention can be used.
(1) Japanese Pat. No. 28,459 issued 12/16/65 by H. Minato (to Teijin Ltd.); C.A. 64, 11090h (1966). PA1 (2) U.S. Pat. No. 3,271,384 issued 9/6/66 to Polaroid Corporation. PA1 (3) British Pat. No. 988,253 issued 4/7/65 to Monsanto Company. PA1 (4) Canadian Pat. No. 750,380 issued 1/10/67 to Monsanto Company. PA1 (5) (a) U.S. Pat. No. 3,278,304 issued 10/11/66 to Gevaert Photo-Production N.V. (b) British Pat. No. 1,054,125 issued 1/4/67 to same assignee. PA1 (1) m is an integer equal to 1-2; PA1 (2) n is a number equal to 1-10; PA1 (3) R' is ##STR3## (4) X is a peroxy containing radical selected from ##STR4## (5) R.sub.1 and R'.sub.1 may be the same or different and are alkyl or cycloalkyl radicals having 1-10 carbon atoms; ##STR5## (7) R.sub.3 is a tertiary aliphatic radical having 4-10 carbon atoms; (8) R.sub.5 and R'.sub.5 may be the same or different and are aliphatic diradicals having 1-20 carbons which diradicals optionally contain in the backbone structure one or more non-adjacent oxygen, sulfur or nitrogen atoms; aromatic diradicals having 6-12 carbons; or aromatic-aliphatic diradicals having 7-20 carbons optionally containing in the backbone structure one or more non-adjacent oxygen, sulfur or nitrogen atoms; PA1 (9) R.sub.6 is a lower alkyl radical (normally containing 1-6 carbon atoms); PA1 (10) R.sub.7 is an alkyl or cycloalkyl radical of 1-10 carbons or an aromatic radical of 6-12 carbons; PA1 (11) R.sub.8 is a lower alkylene diradical (usually having 1-8 carbons); PA1 (12) R.sub.9 is hydrogen, an alkyl or cycloalkyl radical of 1-10 carbons, or an aromatic radical of 6-12 carbons; PA1 (13) R.sub.1 and R.sub.5 together with the tertiary carbon atom in R' can form a cycloalkyl triradical of 3-10 carbons; and PA1 (14) R is (a) a tertiary aliphatic radical of 4-10 carbons, (b) R'-X or (c) R' when m is 1 and X is a diradical. PA1 (1) forming a polymer having azo groups present by reacting vinyl-type monomer and an azo-peroxy compound as above under vinyl polymerization conditions, controlling conditions in order to cause the peroxy-oxygen linkages to rupture prior to rupture of the azo-carbon linkages, said rupture of the peroxy-oxygen linkages having the effect of initiating said polymerization; and PA1 (2) reacting vinyl-type monomer with the polymer of step (1) under conditions to rupture the azo-carbon linkages of said step (1) polymer to produce a block polymer product. PA1 (1) forming a polymer having peroxy groups present by reacting vinyl-type monomer and an azo-peroxy compound as above under vinyl polymerization conditions, controlling the conditions in order to cause the azo-carbon linkages to rupture prior to rupture of the peroxy-oxygen linkages, said rupture of the azo-carbon linkages having the effect of initiating said polymerization; and PA1 (2) reacting vinyl-type monomer with the polymer of step (1) under conditions to rupture the peroxy-oxygen linkages of said step (1) polymer to produce a block polymer product. PA1 X and R.sub.3 are as defined in the aforesaid Summary of the Invention (I. Compounds). PA1 R can be (a) a tertiary aliphatic/radical having 4-10 carbon atoms, particularly a t-alkyl radical, or (b) the combination radical R'-X or (c) when m is 1 and X is a diradical included in the above definition, R can be R'.